Ments



NOV. 19, 1929. R sM|TH 1,736,753

FURNACE REGULATION Original Filed Jan. 19, 1927- 70 OTHER FuRA/A C55Inventor":

Avthur R Sm'HC h,

y His Attorn ey Patented Nov, 1%, 1929 ARTHUR B. SMITH, F

SCHENECTAD'Y, NEW YORK, ASSIGNGR, BY MESNE ASSIGN- MENTS, T0 BAILEYMETER COWANY,

A CORPORATION OF DELAWARE summon naeunarrou Application filed January19, 1927, Serial l lo. 162,198. Renewed April 10, 1929.

The present invention relates to furnaces used to generate elastic fluidor vapor, such as steam, for example.

The object of the invention is to provide an improved automaticregulating system, and, for the consideration of what I believe to benovel and my invention, attention is directed to the accompanyingdescription and the claims appended thereto.

In the drawing, the figure is a diagrammatic view of a system embodyingmy inven tion.

Referring to the drawing, 1 indicates a furnace used to generate steamin a boiler 23. Fuel is supplied to the furnace by a suitable fuelfeeding means 3 such as, for example, a suitable stolrer. The fuelfeeding means is operated by an electric motor at, the arrangement beingsuch that when the speed of the motor increases the amount of the fuelsupplied to the furnace increases, and when the speed of the motordecreases the amount of the fuel supplied to the furnace decreases.

Electric motor 4 is connected to supply lines 5 and 6 by conductors 7and 8. 9 indicates the field of the motor, and in series with it is aregulating resistance 10 adapted to be cut into and out of circuit by aContact arm 13. which is moved by a reversing electric motor 12. Byoperating motor 12 in one direction or the other, the speed of motor ican be varied, and hence the amount of fuel fed to the furnace can beincreased or decreased.

13 indicates a conduit through which the gases, that is, the products ofcombustion, from the furnace are discharged, and 14 indicates a suctionblower for increasing and decreasing the draft on the .furnace. Suctionblower id is driven by electric motor 15 connected to supply lines 5 and(S by conductors 16 and 17. Wluan the speed of motor 15 is increased,the draft on the furnace increased, and when the speed of motor 15decreased, the draft on the furnace is decreased. Suction blower it isto be taken typical oi any suitable means "for regulat ing the quantityof air supplied to the furnace.

18 indicates the field of motor 15, and arm ranged series with it is aregulating resistance 19 adapted to be cut into and out of circuit by acontact arm 20 which is moved by a reversing electric motor 21. Whenmotor 21 is operated in one direction, it serves to sheet an increase inthe speed of motor 15, and hence the quantity of air supplied to thefurnace, while when it is operated in the other directioh it serves toeffect a decrease in the speed of motor 15, and hence decreases theamount of air supplied to the furnace.

22 indicates the steam drum of furnace 1. lit is connected by adischarge conduit 23 to a header 2%., Furnace 1 is one furnace of anumber, all of which supply steam to common header 24;.

25 is an electric flow meter for measuring the amount of air flowingthrough the furnace. it may be of any suitable type. in the presentinstance there is indicated an electric flow meter of the type disclosedin the application of Louis W. Thomson, Serial No. 342,220, filedOctober 27, 1924:. It comprises casing 26 which contains a movableelement which may be in the form of an inverted bell 27, the lower edgeof the bell beingsealed by liquid contained in an annular chamberilti.The opposite sides of bell 27 are connected by trailing and leading;pressure pipes 29 and 30 to a conduit 31 through which air forcombustion purposes is supplied to they furnace. lln conduit 31 is asteam heating coil 32 which may be utilized for heating the air suppliedto the furnace, and in the present instance the air flow meter is shownas having its trailing and leading pipes 29 and 30 con nected onopposite sides or coil 32, the drop in pressure across the coil servingas a measure oi the air flow, as is well understood. Bell 2'? ispivotally connected to a lever 33, one end otwhich is pivoted to a fixedpost 3a. the other end ot" lever 33 is connected by a linlr 35 to anarmature 36., upon which is a closed winding 37. in operative relationto armature 36 is a field structure comprising a winding 38 which isconnected to lead Wires 39 and d0. The tlow meter mechanism illustratedserves to eii'ect oscillating movement oi armature 36 in response tochanges in the rate of flow of air to the boiler, and such oseillatingmovement varies the current in the .rent which is a measure of the airflowing to the furnace.

Conductor 39 is connected to supply line 5.

Conductor 40 is connected to one end of a coil 41 of a balanced relay42, the other end of the coil being connected by a conductor 43 tosupply line 6. There thus flows through c011 41 of balanced relay 42 acurrent proportional to the amount of air flowing to the furnace.

44 indicates. an electrical coal meter for measuring the amount of coalsupplied to the furnace. It may be of any suitable type, the essentialthing being that it produces a flow of electric current which is ameasure of the amount of coal supplied to the furnace. In the presentinstance it is shown as being an instrument of the general type of thatdisclosed in the patent to Thomson & McNairy, No. 1,560,951, patentedNovember 10, 1925. The leg 45 of the meter is connected by a pipe 46 toa device which produces a pressure proportional to the speed at whichthe stoker is driven, and the leg 46 of the instrument is connected by apipe 47 to atmosphere. The pressure applied to the liquid in leg 45effects a deflection of it, causing a fiow of current in the primarywinding 48 of the instrument which is proportional to the pressure andhence to the amount-of fuel supplied'to the furnace; this being the modeof operation of the construction disclosed in the above referred topatent, as is now well understood. The circuit of coal meter 44comprises a conductor 49 which is connected to supply line wire 5 and aconductor 50 which is connected to one'terminal of a coil 51 of relay42. The other terminal of coil 51 is connected by a conductor 52 tosupply'line 6. It will thus be seen that the current flowing in coil 51is one proportional to the amount of fuel-being supplied to boiler 1.Coils 41 and 51 of relay 42 are oppositely wound so that they tend tooppose each other.

Relay 42 has a movable contact 53 which is connected by conductor 54 tosupply line 6,

and two stationary contacts 55 and 56. Contact 55 is connected by aconductor 57 to the field winding 58 of motor 21, and contact 56 isconnected by conductor 59 to field winding 60 of motor 21. Fieldwindings 58 and 60 are connected through the armature of motor 21 tosupply line 5 by conductor 61. With this arrangement when movablecontact 53 engages contact 55 it operates motor 21 in one direction,while when it engages contact 56 it operates motor 21 in the otherdirection.

Connected to header 24 is an electric pressure gage 62 of any suitabletype. In the present instance,' it is indicated as being an instrumentof the same general type as is the coal meter 44; it being understoodthat as a pressure gage it measures a differential pressure, this beingthe difference in pressure between that of the atmosphere and that inheader24. To this end, the leg 63 of the instrument is connected toheader 24 by a pipe 64, and the leg 65 is connected by a pipe 66 toatmosphere. As shown in the drawing, the leg 65 is made long on accountof the comparatively high pressure to be measured. It will be understoodthat the pressure in header 24 maintains a head-of mercury .in leg 65and that as the pressure in the header increases and decreases themercury rises and falls in leg 65. In the casing 67 of the instrument isa transformer element the same as that indicated diagrammatically inconnection with the casing of coal measuring means 44.

With the foregoing arrangement there is produced in the circuit of thepressure gage a flow of current which is proportional to the pressure inheader 24. This circuit coniprises a conductor 68 which is connected tosupply line 5, and a conductor 69 which is connected to one terminal ofa coil 70 which forms a part of a master relay 71. The other terminal ofcoil 70 is connected by a con- I ductor 72 to supply line 6. There isthus produced a flow of current in coil 70 whichis a measure of thepressure in header 24. The electric pressure gage indicated is shownonly by way of example. Any suitable instrument capable of producing aflow of current proportional to pressure may be utilized.

Master relay 71 comprisesamovable contact 73 connected by a conductor 74to supply line 6, and adapted to engage either of two stationarycontacts 75 and 76. Stationary contact 75 is connected by a conductor 77to one of the field windings 80 of motor 12, and contact 76 is connectedby a conductor 81 to the other field winding 82 of motor 12. Motor fieldwindings 80 and 82 are connected through the armature of motor 12 tosupply line 5 by a conductor 83. \Vith this arrangement when movablecontact 73 engages contact 75, motor 12 is operated in one direction,while when it engages contact 76, motor 12 -is operated in the otherdirection.

Relay 71 is a master relay for controlling all the furnaces of a batteryin accordance with an operating condition of the furnaces, the operatingcondition used in the present instance being the pressure in the commonsteam header. 85 indicates connections leading to other furnaces, and 86indicates the balance relay for another of the furnaces which has beendesignated on the drawing furnace No. 2.

Associated with conduit 23 is an electric flow meter in the circuit ofwhich is produced a flow of electric current which is a measure of theflow of steam through conduit 23. Any suitable type of electric flowmeter may be used. A flow meter of the type shown in thebefore-mentioned patent to Thomson & 30 McNairy is indicated in thepresent instance. It comprises a casing 87 having its leading andtrailing legs connected by pipes 88 and 89 to a pressure differencecreating device 90 in steam pipe 23. The circuit of this flow meter isconnected by conductors 91 to a Winding 92 which forms a part of relay42. Thus there is a flow of electric current in winding 92 which bears adefinite relation to the rate of flow of steam through conduit 23. Inother words, the current in coil 92 is proportional to and varies withthe load on boiler 2. Coil 92 is wound in a direction opposite to thatof coil 41, whereby it tends to oppose coil 41. Or, otherwiseconsidered, it is wound in a direction to assist winding 51. Theoperation is as follows: Assume that the various furnaces are burningand that each is supplying vapor through its discharge conduit 23 toheader 24. Assume also that the desired pressure exists in header 24.

Under these circumstances, the current flowing through the coil 70 ofmaster relay 71 will be such as to maintain contact 73 midway betweenstationary contacts 75 and 76, and the various parts will be in thepositions indicated in the drawing. Motor 4 of each furnace will berunning to supply the required amount of fuel to its furnace, and themotor 15 of each furnace will be running to effect the desired supply ofair to its furnace. Assuming also that the desired ratio of fuel to airexists in the case of each furnace, then the flow of current throughcoils 41, 51 and 92 of each balanced relay 42 will be such as tomaintain movable contact 53 midway I bet-ween stationary contacts and56.

If now the pressure in header 24 increases, indicating a decrease indemand for vapor, then pressure gage 67 will be operated to effect anincrease in the amount of current flowing through coil 70 to masterrelay 71. This will cause movable contact 73 to engage one of thestationary contacts 75 or 76, it being assumed in the present instancethat it engages a contact 75. When contact 73 engages contact 75 itcloses a circuit on the field 80 of motor 12, which ma be traced asfollows: supply line 6, con uctor 74, contacts 73 and 75, conductor 77,field winding 80, and conductor 83 to supply line 5. This serves tooperate motor 12 in a direction to decrease the rate of fuel supply tothe furnace. When the rate of fuel supply to the furnace decreases, thecurrent flowing in the fuel meter circuit decreases, whereupon relay 42becomes unbalanced, moving its contact 53 into engagement with one ofthe contacts 55 or 56; for example, contact 55. When contact 53 engagescontact 55 it closes the circuit of the field winding 58 of motor 21,operating motor 21 in a direction to decrease the amount of air suppliedto the furnace, the operation continuing until relay 42 is againbalanced. The decrease in the amount of fuel and air supplied to thefurnace efi'ects a decrease in the amount of vapor generated, .and hencebrings the pressure in header 24 back to normal value, and relay contact73 back to its neutral position.

If the pressure in header 24 decreases, indicating an increase in thedemand for vapor, then master relay 71 is operated to move contact 73into engagement with contact 76, thereby operating motor 12 in adirection to effect an increase in the supply of fuel for furnace. Whenthis occurs, relay 42 becomes unbalanced, contact 53 moving intoengagement with contact 56, and effecting operation of motor 21 in adirection to effect an increase in the amount of air supplied to thefurnace. The increased fuel and air supplied to the furnace serve toeffect an increase in the amount of vapor generated, thereby bringingthe pressure in header 24 back to normal value.

Balance relay 42 serves to maintain at all times the desired ratiobetween the fuel flow and the air flow, and, as will be clear, if at anytime the desired ratio does not obtain, contact 53 will be moved intoengagement with either contact 55 or contact 56 to effect an increase ora decrease in the rate of flow of air to the furnace, the operationcontinuing until the desired fuel-air ratio is ,again established, whencontact 53 will again occu y its central neutral position.

n connection with the operation of a boiler furnace, it is desirable toincrease the ratio of air to fuel with increase in the boiler load, todecrease the ratio of air to fuel with decrease in the boiler load. Thisfunction in" the present instance is performed by the coil 92 connectedto the flow meter which meas ures the flow of vapor through conduit 23.With the arrangement shown, it will be seen that when thesteam flowincreases, coil 92 serves to oppose coil 41 to a greater extent, whichmeans, therefore, that with the same fuel flow a larger proportional airflow is re quired in order to balance the relay. 0n the other hand, upondecrease in the amount of steam flowing in conduit 23, coil 92 opposescoil 41 to a lesser extent, which means that a proportionately smalleramount of air will be required in order to balance the relay. With theabove described arrangement, therefore, it will be seen thatautomatically the ratio of air flow to fuel flow is increased anddecreased with increase and decrease of rap the boiler load. I regardthis as being an important feature of my invention.

In connection with the operation, it should be understood that when thesteam pressure varies in header 24, master relay 71 effects operation ofall the boiler furnaces connected into the system simultaneously. On theother hand, the balance relay 42 of each furnace serves to adjust onlythe fuel and air of the furnace to which it isappurtenant.

The subject matter of claims 9 to 15 herein have been divided out frommy application- Serial No. 82,625, filed January 20, 1926.

In accordance with the provisions of the patent statutes, I havedescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodiment thereof,and I desire to have it understood that the apparatus is onlyillustrative and that the invention is to be carried out by other means.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is:

1. In a furnace control system, the combination of means for supplyingfuel to the furnace, means for supplying air to the furnace, means whichproduces a flow of current which is a measure of the fuel supplied tothe furnace, means which produces a flow of current which is a measureof the air supplied to the furnace, a balanced relay connected to saidtwo last-named means, means responsive to changes in demand on thefurnace for effecting adjustment of the fuel and air in accordance withthe load, said fuel and air beingaadjusted relatively to each otherthrough the intermediary of said bal anced relay, and means formodifying the operation of the balanced relay in accordancc with theload on the furnace.

2. In a furnace control system for a plurality of furnaces, thecombination of means for supplying fuel to each furnace, means forsupplying air to each furnace, means associated with each furnace foreffecting a flow of electric current proportional to the fuel and a flowof current proportional to the air, a balanced relay connected to saidlast-named means, means responsive to changes in the total demand on thefurnaces for effecting adjustment of the fuel and air of each furnace inaccordance with the total load, the fuel and air for each furnace beingadjusted relative'ly to each other through the intermediary of saidbalanced relays, and means for modifying the operation of the balancedrelay of eachfurnace in accordance with theloadon such furnace.

3. In a furnace control system for a plurality of furnaces, thecombination of means for supplying fuel to each furnace, means forsupplying air to each furnace, a' device which changes upon a change inthe total demand on the furnaces, a master relay connected to saiddevice, means controlled by said master relay for regulating the fueland air-supplying means of each furnace, and means for varyingautomatically the fuel-air ratio of each furnace in accordance with theloads on the respective furnaces.

4. In a furnace control system for a plurality of furnaces, thecombination of means for supplying fuel to each furnace, means forsupplying air to each furnace, means associated with each furnace foreffecting a flow of electric current proportional to the fuel and a flowof current proportional to the air, a balanced relay connected to saidlast-named means, a measuring device which produces a flow of electriccurrent which changes upon a change in the total demand on the furnaces,a master relay connected to said measuring device, means controlled bysaid master relay for effecting regulation of the fuel and air to allthe furnaces, the fuel and air to each furnace being adjusted relativelyto each other by said balanced relays, and means for modifying theoperation of said relays in accordance with the load on the furnace withwhich it is associated.

5. The combination with a furnace having means for regulating the amountof air and fuel supplied to it, of a measuring device for effecting aflow of electric current proportional to the air supply, a measuringdevice for effecting a flow of electric current proportional to the fuelsupply, a balanced relay connected to said measuring devices, a deviceresponsive to changes in demand on said furnace. means controlled bysaid last-named device for effecting adjustment of the fuel and air inaccordance with the demand. on the furnace, the air and fuel beingadjusted relatively to each other by said balanced relay, and means formodifying the operation of said relay in accordance with the load on thefurnace.

6. The combination with a furnace having means for supplying fuel andmeans for supplying air thereto, of a control system comprising meanswhich produces aiiow of electric current which is a measure of the fuelsupplied to the furnace, means which produces a flow of electric currentwhich is a measure of the air supplied. to the furnace, a balanced relayconnected to said two lastnamed means, means controlled by said balancedrelay for adjusting the fuel and air relatively to each other, and meansfor modifying the operation of said relay in accordance with the load onthe furnace.

7. The combination with a furnace having automatic means for. varyingthe amount of fuel and air supplied to the furnace in accordance withthe demand on the furnace, of means for maintaining the desired relationwhich produces a flow of electric current between fuel and air for allloads comprising an electric circuit having means therein which effectsa flow of current whlcn 1s a measure of the airflow, an electric circuithaving means therein which effects a flow of current which is a measureof the fuel flow, a balanced relay in said circuits, means controlled bysaid relay for maintaining the desired ratio between fuel and air at allloads, and automatic means responsive to the load on the furnace forvarying the ratio between the fuel and air.

8. The combination with a furnace, of a balanced relay having opposedwindings, means for effecting a flow of current in one of said windingswhich varies with the fuel supplied to the furnace, means for effectinga flow of current in another of said windings which varies with the airsupplied to the .furnace, means for effecting a flow of current inanother of said windings which varies with the load on the furnace, andmeans controlled by said relay for maintaining the desired ratio betweenfuel and air.

9. In a furnace control system, the combination of means for supplyingfuel to the furnace, means for supplying air to the furnace, means.which produces a flow of cur-.

rent which is a measure of the fuel supplied to the furnace, means whichproduces a flow of current which is a measure of the air supplied to thefurnace, a balanced relay connected to said two last-named means, andmeans responsive to changes in demand on the furnace for efiectingadjustment of the fuel and air in accordance with-the load, said fueland air being adjusted relatively to each other through the intermediaryof said balanced relay.

10. In a furnace control system for a plurality of furnaces, thecombination of means for supplying fuel to each furnace, means forsupplying air to each furnace, means associated with each furnace foreffecting a flow of electric current proportional'to the fuel and a flowof current proportional to the air, a balanced relay connected to saidlast-named means, and means responsive to changes in the total demand onthe furnaces for effecting adjustment of the fuel and air of eachfurnace in accordance with the total load, the fuel and air for eachfurnace being adjusted relatively to each other through the intermediarof said balanced relays.

11. In a urnace control system for a plu rality of furnaces, thecombination of means for supplying fuel to each furnace, means forsupplying air to each furnace, means associated with each furnace foreffecting a flow of electric current proportional to the fuel and a flowof current proportional to the air, a balanced relay connected to saidlast-named means, a measuring device which produces a flow of electriccurrent which changes upon a change in the total demand on the furnaces,a master relay connected to said measuring device, and means controlledby said master relay for effecting regulation .and air.

of'the fuel and air to all the furnaces, the

fuel and air to each furnace being adjusted relatively to each other bysaid balanced relays. v

12. The combination with a furnace having means for regulating theamount of air and fuel supplied to it, of a measuring device foreffecting a fiow'of electric current proportional to the air supply, ameasuring device for effecting a flow of electric current proportionalto the fuel supply, a balanced relay connected to said measuringdevices, a device responsive to changes in demand on said furnace, andmeans controlled by said last-named device for effecting adjustment ofthe fuel and air in accordance with the demand on the furnace, the airand fuel being adjusted relatively to each other by said balanced relay.

13. The combination with a furnace having means for supplying fuel andmeans for supplying air thereto, of a control s stem comprising meanswhich produces a ow of electric current which is a measure of the fuelsupplied to the furnace, means which produces a flow of electric currentwhich is a measure of the air supplied to the furnace, a balanced relayconnected to said two last-named means, and means controlled by saidbalanced relay for adjusting the fuel and air relatively to each other.

14. The combination with a furnace having automatic means for varyingthe amount of fuel and air supplied to the furnace in accordance withthe demand on the furnace, of means for maintaining the desired relationbetween fuel and air for all loads comprising an electric circuit havingmeans ing the desired ratio between fuel and air at all loads.

15. The combination with a furnace of a balanced relay havin opposedwindings, means for effecting a do of said windings which varies withthe fuel su plied to the furnace, means-for effecting a ow of current inanother of said windings which varies. with the air supplied to thefurnace, and means controlled by said relay for maintaining the desiredratio between fuel means controlled by said relay for maintain- Inwitness whereof I have hereunto set my w of current in one

